Piston construction



, J' uly 8, 1930. w, -r15 v 1,770,123

PISTON CONS TRUGTION Filed June 5, 1929 E g. 2. J-

Inventor: William I. .Bettz's,

xi ttor-n ey.

Patented July 8, 1930 UNITED STAT S maize PATENT OFFICES warm I. Burris,or nos mamas, carrromna msron consrmrcrrou Application filed nines,-was. Serial 1v. team.

In this ecification, and-the accom anyin' drawin shall describe andshovii a pre ferred orm of my invention, and specifically mentioncertain of its more important objects. I do not limit myself to theforms dis-. closed, since various changes and adaptations may be madetherein without departing. from the essence of my invention ashereinafter claimed; and objects and advantages, other.

than those spec fically mentioned, are included within its scope.

My invention relates in general. to piston construction, andparticularly topistons adapted for use in slush pumps. Among its 'princia1 objects are; fiist, to provide an improve piston construction thatwill remain tight-in slush'pump service, for relatively long periods oftime; second, to provide improved means for ackin PIStOIIS employed insuch service; an ,thir to accomplish the above, and other objects thatwill appear in the following description, in a very simple andrelatively inexpensive manner.

My objects are attained by means of the construction illustratedtypically .in the accompanying drawings, in which-- 7 Figure 1 is alongitudinal section of cylinder, and of a piston therein that'embodiesthe f elements of my invention; and

struction,

Figure 2 is a similar view of a cylinder with the above mentioned pistonshown in elevation and only partially assembled, one

of the packing sleeves being shown broken and pa-rtiallyin cross-sectionfor convenience of disclosure. 4

Similar reference numerals refer to similar parts throughout both viewsIn a com anion application for iston conthat of the present inventionThe latter however embodies additional inventive features, and theclaims of the two applicationsare directed to independent.inventiOns'and do not conflict.

ed May 15,1929, Seria #363,281, I discloseda lpiston having certainfeatures in commonwit The present invention discloses a constructionthat is admirably adapted for securing full advantage of yieldablepackings in such a manner as to resist wear upon either the packa ing orc linder walls for relatively lon periods 0 time. Although it is particuarly adapted to the use of relatively soft rubber packings, it is notconfined to the employment of such material for this urpose, and othersuitable yieldable materia s may be employed in place ofrubber, wheneverthis is found to be desirable.

In the drawings a longitudinal section of'a pump cylinder is shown at 5.Within thi'sis a pump rod 6, carrying a piston head having two conicalexterior surfaces 7 co-axial therewith and tapering toward its resective ends.

In the specific form illustrate the piston head is shown as comprisingtwo hollow cones 8 placed on the piston rod base to base, this beinga'convenient expedient for reducing-its weight and for saving acorresponding amount of material. I

. Surrounding cache-of the conical surfaces of the head is a cylindricalpackingsleeve 9,

purposes of suitable yieldable material such as rubber.

sembled on the piston head, are poncavely tapered, and the smallerdiame't'e'r of the bore of the sleeves at 10, is less than'that of thediameter of the corresponding ortion of conical surfaces 7 u on which tey are to seat.

, Thus, when the s eeves are forced upon the re;

.The bores of these sleeves, before being as spective conical surfacesof the head, their outer ends will be subjected to greater radialcompression than their remainlng portions and they will fit both thepiston head an the cylinder wall most tightly at their outer ends. Thediameter of the bores of the sleeves at their inner faces at 11, isusually made only slightly,-if any, less than the corresponding diameterof the conical surfaces of the heads. Intermediate diameters of thesleeve bores, for a portion of. their axial lengths, are made greater,by means of their concave tapering, than the corresponding d1- ametersof the head surfacesupon which they are to seat. This is to rovide spacewhere into the yieldable material of the sleeves may be distorted, whenradial compressive stresses are imposed upon the sleeves at their endswhen the piston head is forced into their bores. This provision is madefor the well known reason that, although rubber and similar non-porousmaterials are readily distortable, they are nevertheless substantially1ncompressible. If therefore they are to be distorted, space must beprovided for allowin such distortion to take place.

One way of making the concaved conical bore of the sleeves isillustrated in Fig. 2, wherein the right hand sleeve-9 is shown beforeit is forced upon the corresponding conical surface 7 of the head. Itwill be noted that" the bore of the sleeve illustrated in this figurecomprises two portions, of which the inner part 12' is tapered somewhatless than the slope of conical surface 7, andthe outer portion 13 is taered somewhat more. Obviously substantially the same result can be hadby using a spherically concaved bore, in-' stead of the two differentlytapered straight bore portions illustrated. In either case the leastdiameter of the sleeve bores occurs at their outer faces 10, and thisis, as stated of the piston, to retain the cylinder walls and theontheir inner faces,

above, materially less .than that of the correspondin portion of theconical surfaces 7 upon whic they are to seat.

*A' follower plate 14 is provided at each end acking sleeves hesefollower with annular grooves 15 and a plurality of small orifices 16establish communication between said ooves and the outer faces of thecomplete piston. Thus the fluid pressures with- "the cylinder arepermitted to act directly upon theouter faces of the packing sleeves,and will tend to distort the material of the sleeves insuch a way as tofurther compress the yieldable pacln'ng material against the outerportion of conical surfaces 7 I prefer to form my packin sleeves ofsuch'a length that their inner aces .11 will in place when assembled.platesare provided not abut. This will provide an intermediatecircumferential groove. 17 in the completed piston, for the retention offluid that acts as 9.

further aid in making the iston tight in service; such entrapped fluibeing always under a pressure that is intermediate between that in thetwo ends of the cylinder.

I have above described my invention generically, and specifically as tocertain features. It will be obvious to those skilled in the art thatother specific variations may be employed without departing from itsessence.

I- claim as my invention:

1. Piston construction comprising; a piston head having a'taperedperipheral surface co-axial therewith; and a taper-bored cylindricalsleeve of yieldable material surrounding said surface and seatedthereupon; the bore of entrance of the piston head thereinto will causesaid material to be radially compressed; and said compression beinggreatest at the smaller extremity of the bore.

2. Piston construction comprisin a iston head having a conical perlpherasur ace co-axial therewith; and a conically-bored cylindrical sleeve ofyieldable material surrounding said surface and seated thereupon; thetaper of said bore adjacent its smaller extremity being greater thanthat of said peripheral surface; the proportions of the bore being suchthat the entrance ofthe piston head thereinto will cause said materialto be said sleeve being such that the,

radially compresesd; and said compression sion being greatest at saidextremity.

&. Piston construction comprising; a piston head having a taperedripheral surface co-axial therewith; an a taper-bored cylindrical sleeveof yieldable material surrounding said surface and seated thereupon; thebore of said sleeve at its extremities bein less before assembly thanthe diameter 0 the corresponding portions of said surface upon which itis to be seated; the proportions of the bore being such that theentrance of the piston head thereinto will cause said material to beradially compressed; and said compression being'greatest at the'smallerextremity of the bore, and least at intermediate portions.

5. Piston construction comprising; a pieton head having co-axialperipheral surfaces tapered towar its respective ends; and a taper-boredcylindrical sleeve of yieldable material surrounding each ofsaidsurfaces r us VVJLLIAM I. BETTIS.

